My house is 18 years old, (1994) and is still running the original 10 seer outdoor Carrier 2.5 ton AC unit. The original A coil (piston metering) developed a leak last season. I was given (for free) a 5 year old (2007) cased coil that was pulled from another home when they upgraded. It was a 2.5 ton Carrier/Bryant coil, and it fit the same case size, but had a TXV instead of a piston. What are the issues that I should be aware of? The new system does not seem to cool as well, and I have to bump up the airflow by removing some floor registers and return grilles to get the refrigerant flow rate up. How can I tell if the R22 charge or TXV needs adjustment, or if there are other issues with this setup? The temperature in the house is OK, but the unit runs a lot more duty cycle because the supply air is only 6 or 7 degrees cooler than the return air. The person who helped me with this is more familiar with older systems. The furnace/air handler is a 350MAV-036040 Thanks.